This invention relates generally to the packaging of, and electrical, optical and fluidic interconnections to microfluidic, electro-microfluidic, and optical-electro-microfluidic devices.
Microfluidic devices may simultaneously require fluidic, optical and/or electrical interconnection. Within the context of this invention, the terms “microfluidic device”, “electro-microfluidic device”, “optical-microfluidic device”, “optical-electro-microfluidic device” and simply “device”, all refer to devices requiring microfluidic interconnects, and are used interchangeably.
Microfluidic devices, are generally fabricated in silicon, and control or utilize the flow of a fluid (e.g. liquid or gas). Microfluidic devices typically have very small fluidic access ports, e.g. on the order of 100 microns in diameter; have a small overall footprint e.g. 3 mm×6 mm; and are commonly made in silicon using processes developed by the Micro-Electromechanical-Systems (MEMS) and semiconductor integrated circuit (IC) industry. These devices may utilize MEMS elements, e.g. chemical sensors, biosensors, micro-valves, micro-pumps, micro-heaters, micro-pressure transducers, micro-flow sensors, micro-electrophoresis columns for DNA analysis, micro-heat exchangers, micro-chem-lab-on-a-chip, etc. Microfluidic devices have uses in biomedical, chemical analysis, power generation, drop ejection applications and in the production of ink jet printer heads. The latter of which combines electric and fluidic functions on a low-cost, integrated platform. Typically the use of microfluidics in these applications requires the integration of other technologies with the microfluidic devices. For example: optical means may be used to sense genetic content, electronics may be used for chemical sensing, electro-magnetics may be required for electrical power generation, or electrical power may be required for thermal drop ejection.
MEMS microfluidic devices may be fabricated by either bulk micromachining methods, or by surface micromachining technologies. Surface micromachining produces fluidic channel dimensions that are smaller than for bulk micromachining. For example, a typical bulk micromachined channel may have a channel depth of 50 to 100 microns (0.002 to 0.004 inches), whereas a typical surface micromachined channel depth may be on the order of 1 to 5 microns (0.00008 to 0.0002 inches). Making a reliable fluidic connection between two channels having microscale dimensions (e.g. 100 microns or less) is a critical problem. The application of a microfluidic device may require fluidic connection and transitioning from the microscale, e.g. dimensions on the order of 100 microns or less, to the mesoscale, e.g. dimensions on the order of 500 microns, to the macroscale, e.g. dimensions on the order of 1 mm ( 1/16 inch). Where at the macroscale, fluidic interconnections may be made by conventional tubing or SWAGELOK™ (Swagelok, Inc., Solon, Ohio) connectors.
Another difficulty encountered in packaging microfluidic devices is that multiple fluidic interconnections often need to be made in a very small area. For example: Tens of very small (e.g. 10 to 200 micron diameter inlet and outlet ports) fluidic connections may be required within the area of a typical microfluidic device (e.g. on the order of 3 mm×6 mm). These fluidic connections may be closely spaced (e.g. 300 to 500 microns between fluidic connecting ports) and may require precise alignment (on the order of 1 to 10 microns). Attempts to manually assemble multiple micro-fluidic connections, within the required alignment tolerances, can prove difficult, labor-intensive and costly. See for example: Galambos, et. al, “Packaging Dissimilar Materials for Microfluidic Applications”, Proceedings of IMECE'02, 2002 ASME International Mechanical Engineering Congress and Exposition, New Orleans, La., Nov. 17–22, 2002.
What is needed is a system for interconnection to microfluidic devices that can provide; multiple interconnections in a small area, alignment precision on the order of 1 to 10 microns, be leak tight, easy to assemble, chemically resistant, possess a low dead volume, have smooth fluidic transitions, and be low cost to assemble, and be amenable to automated assembly. Additionally what is needed is a packaging approach that can provide microfluidic, electrical and optical interconnections, for integrating fluidic, electrical, optical, and hybrid devices that can contain a combination of functionality.